The present invention is related to bicycle chain transmissions and more particularly to a bicycle chain transmission the arm of force of the pedal crank of which is automatically changed so as to minimize energy consumption in pedaling.
In a regular bicycle chain transmission, a crank is generally fastened in a chain wheel at the center. During pedaling, the arm of force of a crank does not make any change. As it is known that longer arm of force of a crank can minimize energy consumption in forward pedaling. Therefore, there is a kind of chain structure designed in oval shape so that the arm of force of a crank can be automatically changed during its rotation. This type of design can effectively minimize energy consumption in pedaling. However, a chain may be easily disengaged from an oval shape of chain wheel during rotation.